Deep burial as a refuge for lady crabs Ovalipes ocellatus: comparisons with blue crabs Callinectes sapidus

Abstract

Lady crabs Ovalipes ocellatus use a reversed gill current for respiration. Our evidence suggests that this adaptation allows small lady crabs to use deep burial in high energy sand habitats as a refuge from predation unavailable to other species of crabs. In laboratory experiments lady crabs buried deeper into sand than blue crabs Callinectes sapidus, and such burial was shown to protect lady crabs from predation by larger blue crabs. In field experiments lady crabs and blue crabs were tethered and placed in sand and macroalgae (Ulva lactuca)/mud habitats. In the sand habitat more of the small lady crabs s u ~ v e d than the small blue crabs. There was no difference in survival between large crabs of the 2 species. In a rnacroalgae/mud habitat there were no differences in survival between size classes of crabs or between the 2 species of crabs. These data help to explain the distribution of these crabs.